The global shock that followed the UK's vote to leave the EU will dominate the headlines far into the future. The implications are enormous, and will last for years, probably decades.

Yet behind that lurks a crisis threatening a fundamental re-shaping of Britain's politics. The Labour Party is very close to fatal collapse, and only Jeremy Corbyn can prevent it. Right now, he seems determined his party will fall with him.

You can understand the fury of Labour activists. They overwhelmingly elected Corbyn less than a year ago, ignoring the pleas of many of the MPs who have now moved against him.

Why aren't they focusing their fire on the Government? Complaining about the near-total lack of leadership at a time when it is so desperately needed.

Labour MPs acted when they realised an election could be much, much closer than they'd expected. A blundering Remain campaign may have helped bundle the UK out of Europe, but Tory MPs remain convinced they could still annihilate Labour in a snap election.

Even so, the coup would have progressed more slowly had Corbyn not decided to sack Hilary Benn at midnight on Saturday, triggering dozens of resignations, and the overwhelming no confidence vote.

Mr Corbyn is right to say that vote has no constitutional legitimacy under Labour's rules. And he's probably correct in thinking that, if challenged in a leadership election, his army of £3 activists would almost certainly re-appoint him.

But then what?

Eighty-percent of his MPs will not accept his leadership, and will not follow his instructions. Some may decide to split away, forming a Labour Party in exile at Westminster, perhaps becoming the second-largest group in the Commons.

Labour has no god-given right to be one of Britain's main political parties. Right now UKIP is the third biggest party, by share of vote if not parliamentary strength. It's message has been warmly received in Labour's traditional heartlands. It would unquestionably seek to capitalize if Labour is missing in action.

So Mr Corbyn faces a choice. He can, if he wishes, be re-elected by an activist base entirely disconnected from real-world politics. He can continue to ignore anyone who disagrees with him, and spend his time being cheered by crowds certain to endorse his every word.

But if he does, he could destroy his party as well as his own reputation. David Cameron will always be remembered as the leader who took Britain out of the European Union. Jeremy Corbyn must decide if he wants to be the man who destroyed the Labour Party.